1. Field of the Invention
The invention relates to chairs, and more particularly, to chairs capable of tilting and swivelling.
2. Description of the Related Art
An occupant of a chair, such as an office chair, does not remain stationary throughout the course of the day. The occupant is frequently required to change position, whether to move the occupant's spatial position on the floor, or to rotate to face sideward or rearward, or to reach for an object positioned away from the occupant.
To an extent, modern desk chairs address these mobility concerns by providing caster wheels on the base (allowing spatial positioning) and by providing a swivel means immediately below the seat part of the chair (allowing the occupant to face in different directions). However, chair designers have had difficulty addressing the reach concern without compromising the comfort or safety of the occupant.
The ability to move in place while seated is also an ergonomic issue. Certain recent seating improvements have allowed the occupant to tilt in various directions. This moderate degree of mobility is considered important to improve circulation and accommodate the natural “restlessness” of the body, even while seated. Even in stationary chairs, occupants tend to shift their body weight, by leaning from side-to-side and back-and-forth. Stress on the spine and ischia and reduced blood flow to the legs can result if such natural shifting movement is not accommodated in the chair.
While many chairs provide rearward tilting of the seat pan or seat back (or both) to allow the occupant to partially recline, tilting the entire chair at the base more closely mimics the natural shifting movements of the body, using the ankles as a pivot point. The base tilt also allows the occupant's feet to stabilize the chair. However, there is a concern that, in rearward or, especially, in rear-sideward tilting, the occupant may lose control, tilting back (and to the side) too far for the occupant to correct, which may result in the occupant either tipping the chair or falling off the seat, which may lead to injury. It would be beneficial to allow base tilting of the chair in circumscribed degrees to reduce the likelihood of rear-sideward spills.
Such tilting should be accommodated as an additional feature in harmony with other normal functions of a chair, such as swivelling and spring-based “bouncing”.